Starter for electric motors



Oct. 21, 1930. w c OBRHEN 1,779,328

' STARTER FOR ELECTRIC MOTORS Original Filed May 1927 2 SheetsSheet 1 Z a, Z? 5 Z7 Z5 I z; 21/ l6 24 e e 2a 2:. 7 22 l a I 6 c a f 42 5 gwumto'c Oct. 21, 1930. w. c. O'BRIEN 1,779,323 1 STARTER FOR ELECTRIC MOTORS Original Filed May 17, 1927 2 Sheets-Sheet 2 I r I 1 V I 1 1 1 z z ,z/ 1/1 1 Patented Oct. 21, 1930 UNITED STATES WILLIAM C. OBRIEN, OF BALTIMORE, MARYLAND STARTER FOR ELECTRIC MOTORS Application filed May 17, 1927, Serial No. 192,020. Renewed March 15, 1930.

This invention relates to automatic motor starters for electric motors. The purpose of the invention is to provide a starter in which a single magnet operates a main contactor I to close the motor circuits and then operates an armature, provided with retarding means, to close one or more auxiliary contactors which cut the resistance out of the armature circuit of the motor.

In carrying out the invention, I provide a magnet having a core extended outside of its coil and an armature hinged to the core and forming an extension of the same, this armature adapted to swing toward and from the pole-piece of the magnet. I also provide a main contactor, of non-magnetizable metal, which is preferably hinged to swing about the same axis as the armature, and this contactor extends between the armature and the pole-piece. Upon the contactor, on the side facing the pole-piece, I provide a magnetizable plate which is adapted to engage the pole-piece, but is held out of actual contact with the armature bythe bodyofthe main contactor. The magnetic circuit of the magnet extends through the armature and through said plate to the pole-piece. The armature and main contactor are normally held away from the pole-piece by gravity, and when the 0 magnet is energized, the main contactor is immediately drawn toward the pole-piece and closes the circuits through the motor, the magnetizable plate on the contactor adhering to the pole-piece and forming a cap on the 5 same. This movement of the plate toward the pole-piece does not weaken the magnetic circuit through the armature, but, in effect, builds up the pole-piece, bringing it nearer to the armature. The armature is strongly attracted by the pole-piece but its movement toward the same is retarded by any suitable means, and as it moves toward the pole-piece,

it closes one or more auxiliary contactors which cut the resistance out of the armature circuit of the motor. When the magnet is (lo-energized, the armature and main contactor both fall away from the pole-pieceby gravity, assisted by the resilience of the contactors, and the motor circuits are thereby opened and the resistance is included in the armature circuit.

In the accompanying drawing,

Fig. 1 is a front elevation of the starter,- with the parts in normal positions;

Fig. 2 is a side elevation of the same;

Fig. 3 is a top plan view of the same; i

Fig. 4 is a section on the line M of Fig. 1, the main contactor being shown in closed position in full lines and in open position in dotted lines;

Fig. 5 is a side elevation of one of the auxiliary contactors; and,

Fig. 6 is a circuit diagram of the starter.

Referring to the drawing, a represents a suitable base of insulating material, upon which the starter is mounted, Z) indicates the magnet, 0 indicates the armature for operating the auxiliary contactors, (Z indicates the main contactor, and c, c, e and 0 indicate auxiliary contactors.

The core of the magnet is secured to an iron frame 1, having integral posts 2 and 3 which project upwardly at one side of the coil this frame constituting an extension of the magnet core. A pin 5 extends through these posts, and the armature c and contactor (Z are pivotally mounted upon this pin. The armature 0 has lugs 6 at its lower end which fit closely against the post 2, and the shaft 5 extends through these lugs. The armature therefore forms a continuation of the magnet frame. This armature is adapted to swing toward and from the pole-piece 7 of the magnet. A dashpot f retards its movement toward the pole-piece but permits the armature to move freely in the opposite direction. As shown, the dashpot comprises a cylinder 8, pivotally connected to a bracket 9 of nonmagnetic material, which is secured to the posts 2 and 3 of the magnet frame, and a plunger 10, connected by a rod 11 to a fork 12 which projects from a non-magnetic crosspiece 12, secured to the back of the armature 0 at its upper end. The function of the armature c is to operate the auxiliary contactors to cut resistance out of the armature circuit of the motor, as hereinafter described.

The main contactor cl, the function of which is to open and close the motor circuits,

V 50 ing 29. and armature 30 of the motor.

which latter normally lies against the arma-- ture 0, between said armature and the polepiece of the magnet. The arm 13 carries a yielding contact member 15, adapted toen- I 15 gage a stationary line contact 16, which is associated with a blow-out magnet 17; p

The cross-piece 12 projects at bothsides of the armature c, andis provided with adjustable stops 18, 19, 20 and 21-, adapted to 20 engage the auxiliary contactors 6,0, 6 and e respectively. As shown in Figs. 2 and 5, each auxiliary contactor comprises a rectangular frame 22, one side of which is composed in part of a spring 23,'and this frame carries 25 arms 24, which are pivotally mountedupon a pin or shaft 25, supported upon the base a.

A contact 26 on the frame 22 is adapted to engage a stationary contact 27, connected with the resistance of the starter. When the so armature c is moved toward the magnet,the

to its normal position, the auxiliary contactors are released and fall by gravity to their open positions. For starting small motors only one auxiliary contactor may be necessary, While for larger motors, the number of contactors may be-increased to any desired extent. i I i In Fig. 6, a circuit diagram of the starter is shown. In this diagram, the line circuit is indicated at L, L, and a shunt motor is indicated at m. A conductor 28 leads from the side L ofthe supply circuit to'the field wind- The armature circuit proceeds from the armature byconductor 31to the starting resistance 32,

and thence by conductor 33 and connection 3st to the maincontactor cl, and from the stati onary contact 16 through the coil of blowout magnet 17 to theside L of the supply Y circuit. The auxiliary contactors are all connected to theconductor 33 by connections 35,

. as shown, and their stationary contacts 27are connected to the successive sections of the resistance 32, in the usual manner. The field coil 29 of the motor is connected by co'n'ductor 36 to'the main contactor (Z. It Will be evident from an inspection of the diagram 55 that when the main contact-or is closed, the

from the armature and adapted to engage-the 1 circuits through the field and armature of the motor will be completed, the latter circuit including all of the resistances, and that the closing of the auxiliary contactors in succession will cut the sections of resistance out of the armature circuit, in succession. The circuit for the operating magnet 6 extends from conductor28 by conductor 37 to the magnet coil, and thence by conductor 38 through a manually operable switch39 to the'side L of the"supplycircuit. -i/Vh'en the switch 39 is closed, the magnet is energized and when this switch is opened, the magnet is ole-energized. --The operation is as followsz Normally, the parts are in the position shown in Figs. 13, inclusive. When theoperatordesires tostart the motor, he closes the switch 39 and: the mags net 6 thereby becomes energized. :This causes the attraction of the iron plate or armature, affixed to the arm 13 of the main conta-ctor'.cZ,&;85 and said arm instantly moves toward the magnet and closes the motor circuits between the contacts 15 and 16, as indicated in full lines in FigJl. The armature c is also attracted by the magnet, but the movement of thisarrha-seo ture is retarded by the dashpot 7. and this ar;- mature moves slowly toward the magnet, the stops on the cross arm'12 closing thev auxiliary contactors in succession, therebyugradua lly cutting the resistance out of the armature circuit. When it is desired-to stopthe motor, the operator opens the switch 39, thereby causing the magnet b to become daenergized, and

the armature c and contactor (Zfallback to their normal positions, thereby opening the motor circuits and including the resistancein armature circuit. w g V I v I 1 1 tie to be noted thattthe air gap between the armature c and the pole of the magnet is not changed by the movement of the contac- 1 tor from its open to its closed position. The magnetic circuitis completed from the magnet framethrough the armature 0, which constitut'es an extension of said. frame, and

through the iron plate or armature 14, which is interposedbetween the armature cand the pole-piece; If the plate 14 directly engaged the armature 0, it would adhere thereto and the main contactor would not move to closed position independently of: the armature-.0,

but as theplate 14 is spaced from thearmature c and is notconnected to the magnet-frame, the platecan move, with the main contactor, into engagement with the pole-piece independently of the movement of the. armature 0.

l VhatI claimis: i l 1. In a motor starter,.an v ele c'ztromagnet having a pole-piece, an armature movable'toward and from said pole-piece,a mainicontactor of non-magnetizable metal between said armature and pole-piece and movable independently of the armature, said contactor having a magnetizable part interposed'between the armature and pole-piece and spaced pole-piece, means for retarding the move ment of the armature toward the pole-plece, and an auxiliary contactor controlled by said armature.

2. In a motor starter, an electro-magnet having a pole-piece, an armature hinged at one end of the magnet core and forming a continuation of the same, a main contactor of non-magnetiza-ble metal, movable independently of said armature and having a plate of magnetizable metal interposed between said armature and said pole-piece and mechanically held out of engagement with the armature, means for retarding the movement of the armature toward the pole-piece, and an auxiliary contactor controlled by said armature.

3. In a motor starter, an eleotro-magnet having a pole-piece, an armature hinged at one end of the magnet core and forming a continuation of the same, a main contacto-r of non-magnetizable metal hinged to rock about the axis of the armature and extending between said armature and pole-piece and having on its side adjacent the pole-piece a plate of magnetizable metal spaced from said core,

means for retarding the movement of the armature toward the pole-piece, and an auxiliary contactor controlled by said armature.

In testimony whereof I hereunto afiix my signature.

WILLIAM G. OBRIEN. 

